Hydroponic farms are starting to be adopted in the American Pacific Island
for a variety of reasons. There are currently hydroponic operations in Hawaii,
American Samoa, Guam and the Marshall Islands. Many of these operations use cistern
stored rainwater, because of a lark of reliable water supplies, or because of
the quality of available water supplies is unsuitable for hydroponic culture.
Many of these sites are prone to periodic droughts. Thus, sizing. the cistern
is of vital importance to the economic viability of the operation. The cost of
construction of an oversized cistern is an unnecessary expense, while the construction
of an inadequate cistern exposes the operation to a higher risk of a loss of crops.

This paper develops a simple methodology for the optimal sizing of cisterns
given the rainfall history of the site, the water use of the hydroponic system
and the costs of construction. Specific examples are developed for Guam and the
Marshall Islands.